Matcap material in Cycles
To recreate this matcap try to use some Layer Weight nodes. Experiment with the Color Ramp node's modes and slider's placement also.


Here's my nodes setup. I basically added two Emission shaders- one with the white color and the other one with black color. Then used the Layer Weight (Facing) (with different Blend values) and Color Ramp (with different modes- Constant for the bright rim and B-Spline for the blurry interior of the sphere ) nodes.


Here's the test I've done using my low poly gerbil model. The matcap and the render result look almost the same. It is a matter of tweaking some things. If you want to play with the nodes to make the rendered matcap material look perfect here's the .blend: